[R] how to subset rows using regular expression patterns
lzhtom at hotmail.com
Sat Dec 3 12:20:15 CET 2005
i have a dataframe A with several columns(variables). the elements of
column M are character strings. so
i wanna extract all the rows where A$M match some regular expression
for a simple example, let the pattern be just "ab", i wanna subset the rows
where A$M="ab" or "abc" or "abcd" or "abXX".........
i know i can write a loop,using some regular expression pattern functions
like grep row by row. but when A's size is pretty large, it's inefficient.
could anyone give me a hint about a faster code?
thanks a lot!
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